Magnetoresistive Random Access Memory (MRAM) is an emerging technology that may be competitive with prior integrated circuit memory technologies, such as floating gate technology. The MRAM technology may integrate silicon-based electronic components with magnetic tunnel junction technology. A significant element in MRAM is the magnetic tunnel junction (MTJ) where information may be stored. A MTJ stack has at least two magnetic layers separated by a non-magnetic barrier, where a fixed layer has a set magnetic property and a free layer has a programmable magnetic property for storing information. If the fixed layer and the free layer have parallel magnetic poles, the resistance through the MTJ stack is measurably less than if the fixed layer and the free layer have anti-parallel poles, so parallel magnetic poles may be read as a “0” and anti-parallel poles may be read as a “1.” The MTJ stack is typically incorporated into a memory cell, and many memory cells with MTJ stacks are incorporated into a memory bank.
The magnetic properties of the free layer may be changed when the memory cell is programmed, where the alignment of the free layer magnetic properties is changed relative to the fixed layer magnetic properties in the programming process. Programming changes the magnetic properties of the free layer and the fixed layer from anti-parallel to parallel, or from parallel to anti-parallel. The strength of the magnetic properties of the pinned layer impacts the MTJ stack, where stronger magnetic properties produce more reliable information storage. The fixed layer may include a first and second pinned layer, where the first and second pinned layers are magnetically coupled to produce a more robust overall fixed layer. The first and second pinned layers should be crystalline, with the proper type of crystal to support the desired magnetic properties. A seed layer is typically produced underlying the first pinned layer to induce the desired crystallinity. However, the seed layer often requires excessive thicknesses to support the desired crystallinity, where the excessive thicknesses increase the aspect ratio of the MTJ stack and thereby reduce the structural stability of the stack. Furthermore, the seed layer should be thermally robust such that it can withstand annealing, solder reflow processes, or other manufacturing processes.
Accordingly, it is desirable to provide integrated circuits with magnetic tunnel junction stacks having higher thermal robustness and stability, as compared to traditional magnetic tunnel junctions, and methods for producing the same. In addition, it is desirable to provide integrated circuits with improved crystalline structure in the fixed layer, and methods of producing the same. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.